Configurable all-digital coherent demodulator system for spread spectrum applications

ABSTRACT

A configurable all-digital coherent demodulator system for spread spectrum digital communications is disclosed herein. The demodulator system includes an extended and long code demodulator (ELCD) coupled to a traffic channel demodulator (TCD) and a parameter estimator (PE). The demodulator also includes a pilot assisted correction device (PACD) that is coupled to the PE and the TCD. The ELCD provides a code-demodulated signal to the TCD and the PE. In turn, the TCD provides a demodulated output data signal to the PE. The PACD corrects the phase error of the demodulated output data based on an error estimate that is fed forward from the PE. Accumulation operations in the ELCD, TCD, and PE are all programmable. Similarly, a phase delay in the PACD is also programmable to provide synchronization with the error estimate from the PE.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 09/751,783,filed on Dec. 29, 2000, which claims priority to the provisional patentapplication having Ser. No. 60/173,633, filed on Dec. 30, 1999. Eachaforementioned prior application is hereby incorporated by reference inits entirety.

Related applications which are incorporated herein by reference, are:

A CONFIGURABLE MULTIMODE DESPREADER FOR SPREAD SPECTRUM APPLICATIONS

-   Ser. No. 09/751,785, now U.S. Pat. No. 6,934,319.    APPARATUS AND METHOD FOR CALCULATING AND IMPLEMENTING A FIBONACCI    MASK FOR A CODE GENERATOR-   Ser. No. 09/751,776, now U.S. Pat. No. 6,947,468.    A FAST INITIAL ACQUISITION & SEARCH DEVICE FOR A SPREAD SPECTRUM    COMMUNICATION SYSTEM-   Ser. No. 09/751,777, now U.S. Pat. No. 7,031,376.    A CONFIGURABLE CODE GENERATOR SYSTEM FOR SPREAD SPECTRUM    APPLICATIONS-   Ser. No. 09/751,782, now U.S. Pat. No. 6,567,017.    METHOD AND APPARATUS TO SUPPORT MULTISTANDARD, MULTI SERVICE    BASE-STATIONS FOR WIRELESS VOICE AND DATA NETWORKS-   Ser. No. 09/752,050, now U.S. Pat. No. 6,967,999.    IMPROVED APPARATUS AND METHOD FOR MULTI-THREADED SIGNAL PROCESSING-   Ser. No. 09/492,634, filed on Jan. 27, 2000-   Except for application Ser. No. 09/492,634, all of the above    applications are filed simultaneously herewith.

TECHNICAL FIELD

The present claimed invention relates to the field of wirelesscommunication. In particular, the present claimed invention relates toan apparatus and a method for demodulating digital spread-spectrumsignals in a wireless communication system.

BACKGROUND ART

Wireless communication has extensive applications in consumer andbusiness markets. Among the many communication applications/systems are:fixed wireless, unlicensed Federal Communications Commission (FCC)wireless, local area network (LAN), cordless telephony, personal basestation, telemetry, mobile wireless, and other digital spread spectrumcommunication applications. While each of these applications utilizesspread spectrum communications, they generally utilize unique andincompatible modulation and protocols. Consequently, each applicationmay require unique hardware, software, and methodologies fordemodulation. This practice can be costly in terms of design, testing,manufacturing, and infrastructure resources. As a result, a need arisesto overcome the limitations associated with the varied hardware,software, and methodology of demodulating digital signals in each of thevaried spread spectrum applications.

A demodulator component is used in a wireless communication device forcode demodulation and data demodulation of a received signal in order toprovide the data signal. However, the received data signal may haveimpairments due to transmission and propagation delay factors. Thisimpairment can be characterized as multipath fading in which each pathexhibits a random, complex, and time-varying phase delay of the signal.Consequently, a need arises for a receiver to correct the phase error ina received signal.

Pilot signals are used in transmission protocols to help the receiverestimate an unknown channel. Essentially, a pilot signal supportsestimation of an unknown random variable with known data. Coherentdemodulation solves part of the phase error problem by utilizing a pilotsignal having known data, e.g., a pseudonoise (PN) data sequence. The PNdata sequence is known to both the transmitter and the receiver. If thetransmitter sends out a known pilot signal with a known PN sequence,then the receiver can determine the phase correction using an internallygenerated PN sequence that is identical to that of the transmitter. Tocorrect the phase error, a feedback loop can be provided to a radiofrequency/intermediate frequency (RF/IF) transceiver to make phaseadjustments. However, this requires the feedback signal to be in ananalog format. Furthermore, the RF/IF transceiver is an analog deviceutilizing analog components, such as a voltage-controlled oscillators(VCOs) to generate a frequency. These analog components have well-knownweaknesses such as temperature sensitivity, drift, etc. Thus, a needarises for a method and apparatus to overcome the limitations inconventional analog phase correction system.

Because of the nature of a feedback system, a lag in the correction of asignal occurs. That is, the received signal that has passed throughdemodulation prior to the correction does not receive the benefit of thecorrected phase in the RF/IF transceiver. Thus, errors can be propagatedthrough a communication device due to the intermittent phase error andthe lag in the feedback correction system. This error propagation canimpair the quality of service achieved using a communication device.Poor quality of service can have detrimental effects, particularly whenusers demand increasingly stringent performance standards. Furthermore,a feedback system to an analog device can be complicated and costly. Thenature of a feedback system is a closed-loop phase tracking process.Unfortunately, a closed feedback system of this nature is not robust,especially in fading channels. As a result, a need arises for a phasecorrection system that overcomes some of the major limitations of aconventional feedback system.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus that overcomes thelimitations associated with the varied hardware, software, andmethodology of demodulating digital signals in each of the varied spreadspectrum applications. Furthermore, the present invention provides areceiver to correct the phase error in a received signal. Additionally,the present invention overcomes the limitations in conventional analogphase correction system. In particular, the present invention overcomessome of the major limitations of a conventional feedback system.

A first embodiment of the present invention provides a configurabledemodulator system. The demodulator system includes a configurableextended and long code demodulator (ELCD) coupled to a configurabletraffic channel demodulator (TCD) and a configurable parameter estimator(PE). The demodulator also includes a configurable pilot assistedcorrection device (PACD) that is coupled to the PE and the TCD. The ELCDprovides a code-demodulated signal to the TCD and the PE. In turn, theTCD provides a demodulated output data signal to the PE. The PACDcorrects the phase error of the demodulated output data based on anerror estimate that is fed forward from the PE. Accumulation operationsin the ELCD, TCD, and PE are all programmable, or configurable.Similarly, a phase delay in the PACD is also programmable to providesynchronization with the error estimate from the PE.

A second embodiment of the present invention provides a method ofprocessing spread spectrum data using a receiver. The method comprisesseveral steps, the first of which is receiving an analog signal at anRF/IF stage. Next, the analog signal is converted to a digital signalusing an analog-to-digital (A/D) converter. The digital signal is thenfiltered using a chip-matched filter to obtain a complex channel signal.In the next step, the complex channel signal is processed using ademodulator system having a feed forward phase correction signal. Inparticular the last step includes several sub steps, the first of whichdemodulates a user code sequence from the complex channel signal toproduce a code-demodulated sample. The code-demodulated sample iscommunicated to multiple traffic demodulators, each of which demodulatesa different traffic code sequence. In the next step, the demodulatedoutput data sample is communicated to a parameter estimator/pilotassisted correction device pair for each of the plurality of multipathchannels. A phase correction signal is fed forward from each of theparameter estimators to its respective pilot assisted correction device.The phase error of the demodulated output data is corrected at each ofthe pilot assisted correction devices based on the feed forward phasecorrection signal from the parameter estimator.

These and other objects and advantages of the present invention willbecome apparent to those of ordinary skill in the art after having readthe following detailed description of the preferred embodiments, whichare also illustrated in the various drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings included herewith are incorporated in and form a part ofthis specification. The drawings illustrate embodiments of the inventionand, together with the description, serve to explain the principles ofthe invention. It should be understood that the drawings referred to inthis description are not drawn to scale unless specifically noted assuch.

FIG. 1A is a block diagram of a spread spectrum electronic communicationdevice having a feed forward all-digital demodulator system, inaccordance with one embodiment of the present invention.

FIG. 1B is a block diagram of a demodulator block in which theconfigurable demodulator kernel is operated, in accordance with oneembodiment of the present invention.

FIG. 1C is a block diagram of the configurable demodulator kernel, inaccordance with one embodiment of the present invention.

FIG. 1D is a block diagram of an alternative hierarchical arrangement ofcomponents within the configurable demodulator kernel, in accordancewith one embodiment of the present invention.

FIG. 2 is a block diagram of a configurable extended and long codedemodulator (ELCD), in accordance with one embodiment of the presentinvention.

FIG. 3 is a block diagram of a configurable traffic channel demodulator(TCD), in accordance with one embodiment of the present invention.

FIG. 4 is a block diagram of a configurable pilot channel parameterestimator (PCPE), in accordance with one embodiment of the presentinvention.

FIG. 5 is a block diagram of a configurable correction device used tocorrect the phase of a data channel, in accordance with one embodimentof the present invention.

FIG. 6 is a block diagram of a configurable accumulate and dump circuitused in a demodulator, in accordance with one embodiment of the presentinvention.

FIG. 7A is a flowchart of a process to demodulate a signal using anall-digital coherent demodulation with a feed forward correction signal,in accordance with one embodiment of the present invention.

FIG. 7B is a flowchart of a process to demodulate an extended and longcode from a received signal, in accordance with one embodiment of thepresent invention.

FIG. 7C is a flowchart of a process to demodulate a traffic channel codefrom a received signal, in accordance with one embodiment of the presentinvention.

FIG. 7D is a flowchart of a process to estimate parameters of a pilotchannel, in accordance with one embodiment of the present invention.

FIG. 7E is a flowchart of a more detailed process to estimate parametersof a pilot channel, in accordance with one embodiment of the presentinvention.

FIG. 7F is a flowchart of a process to correct phase error in a receivedsignal via a feed forward phase correction signal, in accordance withone embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of theinvention. Examples of the preferred embodiment are illustrated in theaccompanying drawings. While the invention will be described inconjunction with the preferred embodiments, it is understood that theyare not intended to limit the invention to these embodiments. Rather,the invention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention, as defined by the appended claims. Additionally, in thefollowing detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will be apparent toone of ordinary skill in the art that the present invention may bepracticed without these specific details. In other instances, well-knownmethods, procedures, components, and circuits have not been described indetail so as not to unnecessarily obscure aspects of the presentinvention.

The present invention can be implemented in a wide variety of digitalspread-spectrum wireless communication systems or techniques. Thesesystems or techniques include, but are not limited to, fixed wireless,unlicensed Federal Communications Commission (FCC) wireless systems,wireless local area network (W-LAN), cordless telephony, cellulartelephony, personal base station, telemetry, and other digital dataprocessing applications. The present invention can be applied to bothtransmitters, e.g., a base station, and to receivers, e.g., a terminal,for fixed wireless, W-LAN, cellular telephony, and personal base stationapplications.

In particular, one fixed wireless application to which the presentinvention may be applied is a metropolitan multipoint distributionsystem (MMDS). Examples include wireless cable broadcast, or two-waywireless local loop (WLL) systems. Some examples of a W-LAN, that cancommunicates digitized audio and data packets, for which the presentinvention can be applied include Open Air, and the Institute ofElectrical and Electronics Engineers (IEEE) specification 802.11b. Andin the application of unlicensed FCC applications, the present inventionmay be applied to specific instances such as the Industrial, Scientific,and Medical band (ISM) devices, which can include cordless telephonyproducts. Personal base stations can utilize either cordless or cellulartelephony wireless communication standards. Lastly, the cellulartelephony systems in which the present invention can be appliedincludes, but is not limited to, IS-95, IS2000, ARIB, 3GPP-FDD,3GPP-TDD, 3GPP2, 1EXTREME, or other user-defined protocols. The range ofmodulation techniques that are utilized in the exemplary spread spectrumapplications disclosed herein are useful to define the class offunctions for which the present configurable all-digital coherentdemodulator is applicable.

The detailed description of the present invention begins with adescription of a communication device, in FIG. 1A in which aconfigurable all-digital coherent demodulator is implemented. Then, thedetailed description section continues with details of the physicalstructure and architecture of the components of the configurableall-digital coherent demodulator, in FIGS. 1B-1D and FIGS. 2 through 6.Lastly, the detailed description section describes, in FIGS. 7A-7F,various processes associated with the configurable all-digital coherentdemodulator, using exemplary flowcharts.

Communication Device

Referring now to FIG. 1A, a block diagram of an electronic communicationdevice having a feed forward all-digital demodulator system is shown, inaccordance with one embodiment of the present invention. Electroniccommunication device 100 a provides an exemplary application of thepresent invention in a wireless code division multiple access (CDMA)base station. However, the present invention is well suited to use in amobile handset, a test platform, embedded wireless modem, or othercommunication device. Furthermore, the present invention is applicableto any electronic device needing to demodulate a data signal. Thefeed-forward phase correction all-digital demodulator portion of thecommunication system 100 a is described in more detail in subsequenthardware diagrams and flowchart diagrams.

Communication device 100 a includes an antenna 101, a front-endprocessing block 103, a base band processing block 106, a microprocessor(μP)/controller 130, a memory block 120, and a bus 117. Front-endprocessing block 103 is coupled to base band processing block, both ofwhich are coupled to μP 130 and memory block 120 via bus 117.Microprocessor 130 and memory block 120 support the exchange of dataand/or instructions to the various components of communication device100 a.

Front-end processing block 103 is coupled to antenna 101 to receive awireless signal. Front-end processing block includes a radiofrequency/intermediate frequency (RF/IF) transceiver 102, an analog todigital (A/D) converter 104, and a chip-matched filter (CMF) 108,coupled to each other in series. RF/IF transceiver 102 includescomponents such as a voltage-controlled oscillator (VCO), known to oneskilled in the art. A/D converter 104 digitizes the analog signal fromthe RF/IF transceiver 102 into a digital signal in a reception path. Theoutput of CMF 108 can be a complex signal, which is represented byinterconnect 105. Data transmitted within communication device 100 a canbe real only or can be complex, depending upon the application. Thetransfer of real and complex signals can be accomplished by use ofparallel lines for parallel transfer of data or by use of memory buffersand a single line for serial transfer of data. Front-end processingblock 103 is an exemplary embodiment. The present invention is wellsuited to a wide variety of front-end processing components andarchitectures.

Base band processing block 106 processes the recovered digital signalprovided by the front-end processing block 103. Base band processingblock 106 includes at least one pilot assisted demodulator block 110-1through 110-N, CGU 140-1 through 140-N, an allocator 115, and optionaldata processing block 119. A demodulator block 110-1 through 110-Nrefers to a virtual or physical grouping of components per a category,e.g., for application to a given multipath. In the present embodiment,configurable demodulator block 110-1 is repeated in parallel “N” times(where “N” is an arbitrary number) (110-1 through 110-N) in order torealize multipath receiver support D-channel diversity combining. TheD-channel of the N paths is used to realize a multipath-combiningreceiver in the present embodiment. This enables the creation of a rakereceiver for wideband code division multiple access (WCDMA) handsets andbase stations in one embodiment. However, only one configurabledemodulator 110-1 is utilized in another embodiment.

Each demodulator plane 110-1 through 110-N, has its own code generatorunit (CGU), e.g., 140-1 through 140-N respectively, in the presentembodiment. Configurable demodulator block 110-1 and 110-N are coupledto the following components: front-end processing block 103 via line105; allocator 115 via line 107; data processing block 119 via lines144; and are coupled to CGU 140-1 and CGU 140-N via lines 141 a and 141b, respectively. CGUs 140-1 through 140-N provide codes appropriate fordemodulating operations in each of the respective demodulator planes. Inanother embodiment, a single CGU, e.g., 140-1, provides codes tomultiple demodulator planes, e.g., by time-sharing the CGU resources.Data processing block 119 performs functions such as combining,decoding, etc., that are performed by a combiner, a codec device, andother components known by those skilled in the art. These components arenot shown in data processing block 119 for purposes of clarity.

Demodulators 110-1 through 110-N are configurable in terms of whatmodulation and spreading codes they can demodulate, and in terms of therate, or length, over which the modulation occurs at a transmitter.Thus, communication device 100 a receives the following exemplaryconfiguration inputs; extended and long code demodulator (ELCD)observation length 152, traffic code demodulator (TCD) observationlength 154, pilot channel parameter estimator (PCPE) filter length 156,pilot assisted correction device (PACD) delay 158, ELCD codeconfiguration 162, TCD code configuration 164, and PCPE codeconfiguration 166. This configuration information can be received viawired communications with a computing device, e.g., a workstation, inthe present embodiment, or can also be provided by an electronic storagemedium, e.g., CD-ROM, or by wireless transmission, via antenna 101.Configuration information is provided at the time communication device100 a is manufactured and/or initially programmed for operation in thefield, in the present embodiment. However, the configuration informationcan also be dynamically implemented during communication device 100 aoperation in the field. Configuration information is received,processed, and implemented via controller 130 and memory 120 whichcommunicate this information and instruction via bus 117 to base bandprocessor 106. Within base band processor allocator 115 controlsimplementation of configuration information to, and operation of,configurable demodulator blocks 110-1 through 110-N in the presentembodiment. Additional information on the design and implementation ofconfigurations into a configurable communication device is provided inthe above-referenced co-pending U.S. patent application Ser. No.09/492,634, entitled “IMPROVED APPARATUS AND METHOD FOR MULTI-THREADEDSIGNAL PROCESSING.”

Furthermore, because the communication device is configurable toimplement a wide range of demodulator codes in the all-digitaldemodulator, it necessarily follows that a code generator must be ableto provide this wide range of demodulation codes. In one embodiment, aconfigurable code generator unit (CGU) can provide any one of a widevariety of codes and types of codes according to the code configurationrequests received. The wide variety of codes producible by configurableCGU, can include, but is not limited to: multiple types ofchannelization codes, multiply types of traffic codes, multiple types ofuser codes, and/or multiple types of extended codes. Some examples ofcode sequences to which the present invention can be applied include,but are not limited to: M-sequences, Gold codes, S2 codes, etc. Oneembodiment of such a configurable code generator is provided in theabove-referenced U.S. patent application Ser. No. 09/751,782, now U.S.Pat. No. 6,567,017, entitled “A CONFIGURABLE CODE GENERATOR SYSTEM FORSPREAD SPECTRUM APPLICATIONS”. This related application is commonlyassigned, and is hereby incorporated by reference.

Referring now to FIG. 1B, a block diagram of a demodulator block inwhich the configurable demodulator kernel is operated is shown, inaccordance with one embodiment of the present invention. Configurable,or multimode, demodulator block 110-1 includes a local controller 172, aconfigurable demodulator kernel 174, and a memory block 170, in thepresent embodiment. Configurable, or multimode, demodulator kernel 174is a satellite kernel, which is algorithmic-specific in the presentembodiment. That is, while demodulator kernel 174 is a configurableelectronic device capable of performing a wide range of algorithms, thealgorithms are nonetheless limited to the class of demodulatingfunctions. An exemplary description of a multimode demodulator kernel174, e.g., components and coupling arrangements, is provided insubsequent FIGS. 1C and 1D.

Input data line(s) 105 and output data line(s) 144 are coupled toconfigurable demodulator kernel 174 to provide data transfer, in thepresent embodiment. Input data line(s) 105 and output data line(s) 144are implemented as separate lines as shown in FIG. 1B, but can also beimplemented as a bus in another embodiment. In particular, input dataline(s) 105 and output data line(s) 144 provide data streams to and frommultimode demodulator kernel 174 with respect to other kernels orcomponents in the communication device 100 a. Local controller 172provides control and locally scaled clock signals, in one embodiment, toconfigurable demodulator kernel 174, via line 176, to enable datatransfer with minimal input from a global controller, e.g., controller130 of FIG. 1A. The communication mechanism between each kernel isdataflow driven in the present embodiment, but can be control flow, orsome other type of flow in another embodiment.

Controller 172 is a state machine with memory, in the presentembodiment, capable of controlling multimode demodulator kernel 174. Inanother embodiment, controller 172 includes memory that is capable ofpreserving state conditions of at least one configuration of multimodedemodulator kernel 174. Configurable demodulator kernel 174 uses adistributed control and configuration via local controller 172, whicheffectively reduces overhead in terms of instruction fetch and globalcontrol. Configurable demodulator kernel 174 receives system clock input180. Controller 172 and/or memory 170 receive configuration informationfrom configuration line 107, e.g., from allocator 115 of FIG. 1A, in thepresent embodiment. However controller 172 and/or memory 170 receivethis information directly from controller 130 and memory 120 in anotherembodiment. In one embodiment, local controller 172 scales system clockinput 180 to a desired local clock rate for multimode demodulator kernel174. Local clock scaling allows operation of multimode demodulatorkernel 174 at higher rates than the system clock. This allows fortime-sliced methodology, whereby virtual instances of a single hardwareconfigurable demodulator kernel 174 can be implemented to serve multipleusers or channels. States and configurations of configurable demodulatorkernel 174 are swapped to/from memory 170 for each of the time-sliceinstances, via configuration/states line 178. Control/clock line 176provides scaled clock signals, and provides control signals to, andreceives status signals from, multimode demodulator kernel 174, in thepresent embodiment.

Memory block 170 is any type of memory, e.g., random access memory(RAM), a register file, or combination thereof. Memory block 170 storesdata, instructions, states, and/or configuration information forcontroller 172 and/or multimode demodulator kernel 174, in the presentembodiment. Memory block 170 is coupled to receive configurationinformation, e.g., PCPE code configuration 166, and demodulatorobservation length 154 as shown in FIG. 1A, via configuration line 178.Memory block 170 includes static registers, which are fixed atinitialization, in the present embodiment. However, the presentinvention is well suited to utilizing dynamic registers in memory block170 that can be updated internally and on the fly by other componentswithin a communication device, e.g., by local controller 172. Memory 170passes configuration and state information to multimode demodulatorkernel 174 via interconnect 178.

By having local memory block 170 and local controller 172, configurabledemodulator kernel 174 is an autonomous device in the presentembodiment. This arrangement provides a very quick and efficientchanging of configuration data for algorithmic satellite kernel, ormultimode demodulator kernel, 174. Therefore, time-sharing of a hardwarekernel is feasible and practical.

Configurable demodulator kernel 174 of FIG. 1B is well suited toalternative embodiments. For example, system controller can providecontrol functions to multimode demodulator kernel 174, thus eliminatinglocal controller 172. In another alternative, memory block 170 can beany form of memory, such as registers, flash memory, etc.

Referring now to FIG. 1C, a block diagram of the configurabledemodulator kernel is shown, in accordance with one embodiment of thepresent invention. FIG. 1C provides one configuration of the demodulatorblocks included within an exemplary demodulator kernel 174-1 applicablein configurable demodulator 110-1 of FIG. 1B and in exemplarycommunication device 100 a of FIG. 1A.

Configurable demodulator block 174-1 is an exemplary configuration thatcan be applied to each of the multiple configurable demodulator blocks110-1 through 110-N. Included within configurable demodulator kernel174-1 are a configurable extended and long code demodulator (ELCD) 112,a configurable traffic channel demodulator (TCD) 114, a configurablepilot channel parameter estimator (PCPE) 116, and a configurable pilotassisted correction device (PACD) 118. TCD 114 and PCPE 116 are coupledin parallel to both PACD 118, via lines 184 and 186 respectively, andare coupled to ELCD 112 by common lines 180/182. These demodulatorcomponents 112-118 coherently demodulate the digital data in both codeand data. In particular, the coherent demodulation includes extended andlong code demodulation, as well as coherent traffic channel demodulationvia pilot-channel assist. Additional description of the operation ofconfigurable demodulator block 174-1 is provided in subsequentflowcharts 7000-8500.

Notably, PCPE 116 is coupled to PACD 118 via feed forward line 186 toprovide a digital feed forward phase correction signal for thedemodulated output data sample. In this manner, the present inventionprovides a phase correction signal that is specific to a given signal,e.g., multipath, on a configurable demodulator plane 110-1. Thus, thepresent invention overcomes the limitation of providing a compositesignal based on the phase offset averaged from multiple demodulationcircuits, some of which may be contradictory. Additionally, the presentinvention corrects the phase of a data signal in real time, provided thephase correction signal and the data signal for which it was calculatedare synchronized. Thus, the present invention overcomes the limitationof a conventional feedback phase correction system wherein data signalsare corrected for a past phase error, e.g., due to feedback timing. As aresult, the fidelity of the data signal is much greater than that of aconventional feedback system.

The specific configuration of ELCD 112, TCD 114, PCPE 116, and PACD 118of base band processing block 106 is chosen to instantiate a specificembodiment of a signal transmission technique. The specific signaltransmission technique utilized for the present invention uses a spreadspectrum transmission technique having a code-multiplexed pilot signal.The transmitter includes a traffic channel, W_(d), that is built, forexample, on the short Walsh code, and a code-multiplexed pilot channelW_(p) that is also built, for example, on the short Walsh code.Typically, based on the transmission environment, the energy devoted tothe pilot channel can vary. The two channels (in-phase andquadrature-phase) are then code multiplexed to create the baselinecomplex physical channel. This baseline channel is then pseudonoise (PN)modulated with a user's unique long PN code (a real number), denoted asC_(PNLong), followed by PN modulation by a complex extended PN sequence,denoted as C_(p)+jC_(q). The resulting complex channel is fed into atransmit chip pulse shaping filter, followed by an IQ carrier modulator.While the present embodiment is applicable to this specific transmissiontechnique, the present invention is well suited to accommodating a widerange of signal transmission techniques. Some of these alternativesignal transmission techniques may dictate more or less components, ormay dictate alterative coupling arrangements, than the presentembodiment. However, the concept of the present invention is stillapplicable to these alternative embodiments.

Those skilled in the art will recognize numerous advantages associatedwith the disclosed technology. These advantages include: (1) separationof traffic and pilot channel demodulators using pure feed-forwardtechniques; (2) realization of an multiple phase shift key (MPSK) pilotchannel using a non-interpolative parameter estimator; (3) a demodulatorarchitecture that can be programmed for different user, group, and longcode configurations for WCDMA; (4) a demodulator architecture that canbe parameterized according to system and channel conditions to achievenear-ideal performance via quasi-coherent reception; (5) a demodulatorarchitecture that can employ a pilot-assisted method for coherentdetection for systems with code-multiplexed pilot channels; (6) alow-complexity implementation of a coherent demodulator for WCDMA; and(7) a demodulator architecture that can be configured to operate in anystandard using CDMA with MPSK modulation and a code-multiplexed pilot.Furthermore, the new architecture represents a single datapath that canbe configured to multiple standards that employ the principle ofcode-multiplexed pilot signals, thereby reducing circuitry. This newarchitecture offers a very low-complexity approach to design ofquasi-coherent demodulators. The feed forward nature of the architectureallows for robust performance in fast-changing mobile radioenvironments.

Referring now to FIG. 1D, a block diagram of an alternative hierarchicalarrangement of components within the configurable demodulator kernel isshown, in accordance with one embodiment of the present invention.Configurable demodulator kernel 174-2 has many components and couplingarrangements that are similar to those presented in configurabledemodulator kernel 174-1 of FIG. 1C. For purposes of clarity, only adescription of components, coupling arrangements, and alternativeembodiments for FIG. 1D that are different from FIG. 1C will be providedherein. Otherwise, the description of components, coupling arrangementsand alternatives provided in FIG. 1C apply similarly to FIG. 1D.

Notably, configurable demodulator kernel 174-2 utilizes a single ELCD112 in base band block to provide signals to the multiple trafficchannel planes 113-1 through 113-M, and the subsequent multipledemodulator planes 111-1 through 111-N, used for multipath signals Thisconfiguration is chosen for the present embodiment to eliminate hardwarerepetition, thus saving power and integrated circuit area. Inparticular, the extended and long code will be the same for a given userin a communication device. Thus, only a single ELCD 112 can be used tosupply all the traffic channel planes 113-1 through 113-M configurabledemodulator kernel 174-2. However, if multiple users exist incommunication device 100 b, then multiple user planes can be utilized,e.g., one user plane for each user. A user plane is a figurativegrouping of an ELCD, e.g., ELCD 112, and traffic channel planes, e.g.,113-1 through 113-M, along with their respective multipath demodulatorplanes, e.g. 111-1 through 111-N. The value of N and M is arbitrary andcan span a wide range of values.

Similarly, only a single TCD, e.g., TCD 114 a, is utilized for multipledemodulator planes, e.g., planes 111-1 through 111-N, in a given trafficchannel plane, e.g., 113-1. This configuration is chosen for the presentembodiment to eliminate hardware repetition, thus saving power andsilicon area. In particular, the traffic channel code will be the samefor all multipaths within that traffic channel. Thus, only a singletraffic channel demodulator 114 a can be used to supply all themultipaths with the signal.

Components of Pilot-Assisted Configurable All-Digital Demodulator

FIGS. 2 through 6 illustrate the physical structure and architecture ofthe configurable components of the configurable all-digital coherentdemodulator. The components are presented as individual demodulatorblocks that link together to form the configurable all-digitaldemodulator. FIGS. 7A-7F are flowcharts of the processes associated withthe components of the configurable all-digital coherent demodulator.

Referring now to FIG. 2, a block diagram of a configurable extended andlong code demodulator (ELCD) is shown, in accordance with one embodimentof the present invention. ELCD 112 of FIG. 2 provides an exemplaryextended and long code sequence demodulator for application inconfigurable demodulator kernels 174-1 and 174-2 of FIGS. 1C and 1D,respectively.

ELCD 112 essentially has two parallel branches, one for the in-phaseportion of the signal, and one for the imaginary portion of the signal.In particular, ELCD 112 has a first multiply-logic device 200 and asecond multiply-logic device 201, both of which are coupled to input105. Multiply logic device 200 has an input to receive a code sequence162 a, C_(PN)(n)C_(p), which is a product code of a unique longpseudonoise (PN) sequence, C_(PN)(n) for user ‘n’ and an in-phaseportion, C_(p), of a complex extended PN sequence. Similarly,multiply-logic device 201 has an input to receive a code sequence 162 b,C_(PN)(n)C_(q), which is a product of the same unique long pseudonoise(PN) sequence and a quadrature-phase portion, C_(q), of a complexextended PN sequence. In the present embodiment, ELCD 112 can demodulateany extended and long code sequence, given the appropriate configurationinstructions, e.g., ELCD code configuration input 162 of FIG. 1A thatspecifies the ELCD code sequence input 162 a and 162 b.

Sum and dump, or accumulator, circuits 204 and 205, are coupled tomultiply-logic devices 200 and 201, respectively. Both sum and dumpcircuits 204 and 205 have inputs to receive an observation length 152that establishes the number of sum operations required before a dumpoperation is performed. Thus, sum and dump circuits 204 and 205 have aconfigurable accumulate, or integration, length. In this manner, thepresent invention allows ELCD 112 to be configured for a given user,application, and/or performance level. Sum and dump circuits 204 and 205provide a real, e.g., in-phase, code demodulated sample on line 180 anda complex, e.g., quadrature-phase, code demodulated sample on line 182,respectively. Output lines 180 and 182 are coupled in parallel to TCD114 and to PCPE 116, as shown in previous FIGS. 1C and 1D, and insubsequent FIGS. 3 and 4. First accumulator 204 and the secondaccumulator 205 each have separate add-logic devices for adding thein-phase portion and the quadrature-phase portion of a signal.Additional details of configurable-length accumulators are provided inFIG. 6.

Notably, ELCD 112 can include configurable sub components andcross-coupling that allow different combinations of multiplicationoperations to be performed between the in-phase and quadrature-phasechannel signal on line 105 and the in-phase and quadrature-phase codesequence inputs 162 a and 162 b. This configurability provides thepresent invention with an even greater scope of accommodating multipletransmission despreading and demodulating techniques. One embodiment ofsuch a configurable sub component is provided in the above-referencedU.S. patent application Ser. No. 09/751,785, now U.S. Pat. No.6,934,319, entitled “A CONFIGURABLE MULTIMODE DESPREADER FOR SPREADSPECTRUM APPLICATIONS”.

Referring now to FIG. 3, a block diagram of a configurable trafficchannel demodulator (TCD) is shown, in accordance with one embodiment ofthe present invention. TCD 114 of FIG. 3 provides an exemplary trafficchannel demodulator for application in configurable demodulator kernels174-1 and 174-2 of FIGS. 1C and 1D, respectively. TCD 114 receives codedemodulated samples, on lines 180 and 182, from ELCD 112 and performssample energy accumulation operations and multiple phase shift keying(MPSK) operations to produce a demodulated output data sample, on line184, which has not been corrected for phase errors. The operation of TCD114 is described in more detail in a subsequent flowchart.

TCD 114 essentially has two parallel branches, one for operations toobtain a real sample, and one for operations to obtain aquadrature-phase sample. In particular, TCD 114 includes a firstmultiply-logic device 302 on one branch that is coupled to input line180, whose source is ELCD 112 of FIG. 2. Similarly, TCD 114 includes asecond multiply-logic device 304 on another branch that is coupled toinput line 182, whose source is ELCD 112 of FIG. 2. Both multiply logicdevices 302 and 304 have inputs to receive a traffic code sequence 164a. TCD 114 can demodulate any traffic channel code sequence, given theappropriate configuration instructions, e.g. TCD code configurationinput 164 of FIG. 1 that specifies the TCD code sequence input 164 a. Inthe present embodiment, traffic code sequence input 164 a is a W_(d)that is based on a short Walsh code. However, traffic code sequenceinput 164 a can be based on another code sequence in another embodiment.

A first sum and dump, or accumulator, circuit 306 is coupled tomultiply-logic device 302, while a second sum and dump, or accumulator,circuit 308 is coupled to multiply-logic device 304. Both sum and dumpcircuits 306 and 308 have inputs to receive an observation length 154that establishes the number of sum operations required before a dumpoperation is performed on an in-phase portion and a quadrature-phaseportion of the sum. Thus, sum and dump circuits 306 and 308 have aconfigurable accumulate, or integration, length. In this manner, thepresent invention allows TCD 114 to be configured for a given user,application, and/or performance level. First accumulator 306 and thesecond accumulator 308 each have separate add-logic devices for addingthe in-phase portion and the quadrature-phase-phase portion of a signal.Additional details of configurable-length accumulators are provided inFIG. 6.

TCD 114 also includes a first adder-logic device 310 coupled to anoutput for an in-phase signal from first sum and dump circuit 306 andcoupled to an output for a quadrature-phase signal from second sum anddump circuit 308. In a complementary manner, TCD 114 includes a secondadder-logic device 312 coupled to an output for a quadrature-phasesignal from first sum and dump circuit 306 and coupled to an output fora real signal from second sum and dump circuit 308. Outputs from firstadder-logic device 310 and second adder-logic device 312 are coupled toan interface 314 that provides a demodulated output data sample on line184 to a subsequent block. Interface 314 can include a memory buffer andcircuitry for serial transmission of the in-phase and quadrature-phaseportions of signals received from first adder-logic device 310 and fromsecond adder-logic device 312. Alternatively, interface 314 can be a busof parallel lines, one for the in-phase portion of the signal and onefor the quadrature-phase portion of the signal. This configurationapplies to other interfaces in configurable demodulator 110-1.

Referring now to FIG. 4, a block diagram of a configurable pilot channelparameter estimator (PCPE) 116 is shown, in accordance with oneembodiment of the present invention. PCPE 116 provides an exemplarypilot channel parameter estimator for application in configurabledemodulator kernels 174-1 and 174-2 of FIGS. 1C and 1D, respectively.PCPE 116 receives code demodulated samples, on lines 180 and 182, fromELCD 112 and performs an open-loop phase estimation in an open-loopchannel estimator 407, followed by a filtering operation in filters 416and 418 to produce a phase correction signal based on the pilot channelphase error, on line 186. The operation of PCPE 116 is described in moredetail in a subsequent flowchart.

PCPE 116 essentially has two parallel branches in open-loop channelestimator 407 and with respect to filters 416 and 418, one foroperations to obtain an in-phase sample, and one for operations toobtain a quadrature-phase sample. In particular, open loop channelestimator 407 includes a first multiply-logic device 402, e.g., on onebranch, coupled to input line 180, whose source is ELCD 112 of FIG. 2.Similarly, PCPE 116 includes a second multiply-logic device 404, e.g.,on another branch, coupled to input line 182, whose source is also ELCD112 of FIG. 2. Both multiply logic devices 402 and 404 have inputs toreceive a pilot channel code sequence 166 a. PCPE 116 can demodulate anypilot channel code sequence, given the appropriate configurationinstructions, e.g., PCPE code configuration input 166 of FIG. 1 thatspecifies the code sequence input 166 a. In the present embodiment,pilot channel code sequence input 166 a, W_(p), is based on a shortWalsh code. However, pilot channel code sequence input 166 a can bebased on another code in an alternative embodiment. Multiply-logicdevice 402 is coupled to a first interface circuit 406 to transfer afirst pilot demodulated sequence, while multiply-logic device 404 iscoupled to a second interface circuit 408 to transfer a second pilotdemodulated sequence. Both interface circuits 406 and 408 provideseparate in-phase (I) and quadrature-phase (Q) output lines of thecomplex signal that is input to them from multipliers 402 and 404,respectively.

PCPE 116 also includes a first adder-logic device 410 coupled to anoutput for an in-phase signal from first interface 406, andcross-coupled to an output for a quadrature-phase signal from secondinterface 408. In a complementary manner, PCPE 116 also includes asecond adder-logic device 412 cross-coupled to an output for aquadrature-phase signal from first interface 406, and coupled to anoutput for an in-phase signal from second interface 408.

A first sum and dump, or filter, circuit 416 is coupled to first adder410, while a second sum and dump, or filter, circuit 418 is coupled tosecond adder 412. Both first filter 416 and second filter 418 have aninput for receiving a filter length 156 that establishes the number ofsum operations required before a dump operation is performed. Thus,filters 416 and 418 have a configurable filter, or integration, length.In this manner, the present invention allows a parameter estimator,e.g., for a pilot signal, to be configured for a given user,application, and/or performance level. Filters 416 and 418 areconfigured for a finite impulse response (FIR) operation in the presentembodiment, but can be configured for an infinite impulse response (IIR)operation in another embodiment. Both filter configurations are known bythose skilled in the art. Additional details on a configurable-lengthaccumulator, or filter, are provided in FIG. 6. First filter circuit 416and second filter circuit 418 are coupled to an interface 426 thatprovides the in-phase and quadrature-phase portions of signals fromfilters 416 and 418 to subsequent block via line 186. Interface 426 hassimilar components and functions as interface 314 of FIG. 3.

Referring now to FIG. 5, a block diagram of a configurable pilotassisted correction device (PACD) 118 used to correct phase of a datachannel is shown, in accordance with one embodiment of the presentinvention. Configurable PACD 118 provides an exemplary correction devicefor application in configurable demodulator kernels 174-1 and 174-2 ofFIGS. 1C and 1D, respectively. PACD 118 implements the phase correctionsignal from PCPE 116 on demodulated output data sample from TCD 114. Theoperation of PCPE 116 is described in more detail in a subsequentflowchart.

PACD 118 includes a delay buffer, Z^(−D) 502 coupled to a multiplierlogic device 506. In turn, multiplier logic device 506 is coupled to aninterface 508 via line 186 to feed forward a phase-corrected datasignal. The power “−D” refers to the amount of delay, in cycles or timethat is accommodated in delay buffer 502. Delay buffer 502 includesmemory buffer hardware, e.g., a variable tap delay line, which can storedata. An input to delay buffer 502 receives a delay value 158 thatestablishes the amount of delay, e.g., quantity of cycles, betweenreceiving a sample on input line 184 and transmitting the sample tomultiply-logic device 506. Thus, PACD 118 has a configurable filter, orintegration, length. In this manner, the present invention allows aparameter estimator, e.g., for a pilot signal, to be configured for agiven user, application, and/or performance level. Delay buffer 502 hasan input 184 coupled to TCD 114 for receiving a demodulated output datasample. And multiplier has an input 186 coupled to PCPE 116 forreceiving a feed forward phase error correction signal.

Real buffer 508 also includes memory buffer hardware for storing phasecorrected in-phase and quadrature-phase data that is subsequentlycommunicated to processing block 119 of FIG. 1A for subsequentoperations, e.g., decoding. Buffer 508 has an output line 144 coupled todata processing block 119, as shown in FIG. 1C for providing the realsignal for subsequent operations. In this manner, real or m-ary phasedata can be provided and interpreted by subsequent data processing block119.

Referring now to FIG. 6, a block diagram of a configurable accumulateand dump circuit used in a demodulator is shown, in accordance with oneembodiment of the present invention. FIG. 6 provides an exemplaryconfigurable accumulate and dump circuit 306 for TCD 114 of FIG. 3.However, the components in configurable accumulate (or sum) and dumpcircuit 306 that provide the comparison and enable logic are equallyapplicable to: 1) configurable accumulator circuits 204 and 205 for ELCD112 of FIG. 2; 2) configurable filter circuits 416 and 418 for PCPE 118of FIG. 4; and 3) configurable delay buffer 502 for PACD 118. Thedetailed operation of configurable accumulate and dump circuit 306 isdescribed in more detail in a subsequent flowchart.

Configurable accumulate and dump circuit 306 includes a comparator 656,a counter 654, and a dump length block 652. Dump length block 652, e.g.,a memory register, has an input line for receiving a configurableobservation length 154. Counter 654 is a device known to those skilledin the art for counting clock cycles. Counter 654 has an input line forreceiving a local clock cycle input 176 a, e.g., as provided by clockline 176 from local controller 172 of FIG. 1B. Comparator 656 is coupledto both counter 654 and dump length block 652 for purposes of comparingthe clock cycle count in counter 654 with the dump length value storedin memory register 652 and providing an enabling signal on enable line660. Enable line is coupled to an integrator circuit 658 to enable achange in state, e.g., a dump and reset operation.

While configurable accumulate and dump circuit 306 of FIG. 6 providesspecific hardware for functions such as counter and comparator, thepresent invention is well suited to using alternative hardware such as alocal base band controller. Furthermore, while configurable accumulateand dump circuit 306 of FIG. 6 provides a separate dump length block652, comparator 656, and counter 654 for a single integrator circuit658, the present invention is well suited to having multiple integratorcircuits coupled to comparator. For example, integrator circuit 658 ofconfigurable dump circuit 306 and integrator circuit (not shown) ofconfigurable dump circuit 308 can both be coupled to comparator 656 forpurposes of receiving an enable signal for a dump and reset operation.Because the two branches of TCD 114 operate in parallel on the sameclock cycle in the present embodiment, they would both be controlled bythe single enable signal.

FIGS. 3-6 utilize multiply, add, accumulate, interface, buffer, andfilter circuits, that are multi-bit wide devices in the presentembodiment, e.g., for performing multiply, operations on multi-bitentities, e.g., a bit word of any length. However, they can also besingle bit width devices in another embodiment. Furthermore, the resultsprovided from accumulate operations can be varying levels of bitgroupings, ranging from chips to symbols or a portion thereof, to a dataframe or a portion thereof, to a slot or portion thereof, and to a fieldor a portion thereof. Thus, after each accumulate and dump operation,the resultant sequence or sample can be labeled to one of thesegroupings. Multiply and add logic devices of FIGS. 3-5, e.g., 302, 402,and 506, respectively, handle operations on the in-phase andquadrature-phase portion of a signal using two-input AND gates forperforming two-bit math operations in the present embodiment. However,multiply logic devices 302 and 304 can be implemented using a differentgate device, e.g., an X-OR gate for a multiply operation on amultiple-bit sample.

Processes for Configurable All-Digital Coherent Demodulation

The following detailed description for FIG. 7A provides a flowchartembodiment of the processes associated with the communication deviceembodiments of FIGS. 1A through 1D. The detailed description for FIGS.7B through 7F provides flowchart embodiments of the processes associatedwith components of the configurable all-digital coherent demodulator.Flowcharts 7000 through 7500 are implemented using the exemplaryhardware diagrams of FIG. 1A through FIG. 6. While FIGS. 7A through 7Faccommodate complex signals, e.g., having an in-phase and aquadrature-phase component, the present invention is well suited tousing only real signals, e.g., utilizing the in-phase portion andneglecting the unused quadrature-phase component. Furthermore, thepresent invention is well suited to using any one of multiple forms ofcomplex signals, e.g., BPSK, MPSK, QAM, etc. The reference to samples asoutput from different demodulator blocks, e.g., ELCD, TCD, depends uponthe utilization of a given block and depends upon the configurableaccumulation lengths utilized. These variables will determine for agiven configuration input, whether the samples from each demodulatorblock are classified as a symbol, a field, a slot, and a frame.

Referring now to FIG. 7A, a flowchart of a process to demodulate asignal using an all-digital coherent demodulation with a feed forwardcorrection signal is shown, in accordance with one embodiment of thepresent invention. Flowchart 7000 can effectively be used to demodulateinput data by using a wide range of demodulation schemes. Furthermore,flowchart 7000 can effectively be programmed to implement a wide rangeof future proprietary algorithms by virtue of the configurable functionsand parameters. Flowchart 7000 is implemented primarily in communicationdevice 100 a of FIG. 1A, with more detailed descriptions of the processprovided in subsequent flowcharts and implemented in component FIGS.2-6.

Flowchart 7000 begins with step 7002. In step 7002 of the presentembodiment, an analog signal is received. Step 7002 is implemented, inone embodiment using antenna 101 and radio frequency (RF) intermediatefrequency (RF/IF) transceiver 102 of FIG. 1A. Antenna 101 and RF/IFtransceiver 102 receive a wireless analog signal and perform signalmixing, filtering and gain control functions, respectively, as known tothose skilled in the art. Following step 7002, flowchart 7000 proceedsto step 7004.

In step 7004 of the present embodiment, an analog signal is converted toa digital signal. Step 7002 is implemented, in one embodiment, by A/Dconverter 104. In particular, A/D converter 104 digitizes the analogsignal from the RF transceiver 102 into a digital signal in a receptionpath. Following step 7004, flowchart 7000 proceeds to step 7006.

In step 7006 of the present embodiment, a digital signal is filtered ina chip-matched filter. Step 7002 is implemented, in one embodiment, chipmatched filter (CMF) 108 matches the signal to a chip pulse shapesuitable for subsequent processing in base band processing block 106 ofFIG. 1A. The output of CMF 108 can be a complex signal, which isrepresented by the wide interconnect 105. Following step 7006, flowchart7000 proceeds to step 7008.

In step 7008 of the present embodiment, a user and/or extended codesequence is demodulated. Step 7008 is implemented, in one embodiment,using a quantity and placement of extended and long-code demodulator(ELCD) 112 as shown in FIGS. 1C and 1D. Likewise, one embodiment of thecomposition of ELCD 112 is provided in FIG. 2. While the presentembodiment utilizes a product of user and extended code, anotherembodiment can only utilize a user code. Step 7008 is described in moredetail, in one embodiment, in subsequent flowchart 7100 of FIG. 7B.Following step 7008, flowchart 7000 proceeds to step 7010.

In step 7010 of the present embodiment, a code-demodulated sample iscommunicated to traffic demodulator(s) (TCD) and to a pilot channelparameter estimator (PCPE). Step 7010 is implemented, in one embodimentby communicating a first code-demodulated sample, e.g., an in-phaseportion of the code demodulated sample, via line 180 to both TCD 114 andPCPE 116 for further processing. Similarly, a second code demodulatedsample, e.g., a complex portion of the code demodulated sample, iscommunicated via line 182 to both TCD 114 and PCPE 116 for furtherprocessing. Following step 7010, flowchart 7000 proceeds to step 7012.

In step 7012 of the present embodiment, a traffic channel isdemodulated. Step 7012 is implemented, in one embodiment, using trafficchannel demodulator (TCD) 114 coupled in communication device as shownin FIGS. 1C and 1D. FIG. 1D provides for the communication protocolwhere a single user has multiple traffic channels, thus requiring asingle user demodulation step/device with subsequent multiple trafficchannel demodulation steps/devices. Likewise, one embodiment of thecomposition of TCD 114 is provided in FIG. 2. While the presentembodiment utilizes a product of user and extended code for demodulatingthe traffic code, another embodiment can utilize only a user code. Step7012 is described in more detail, in one embodiment, in subsequentflowchart 7200 of FIG. 7C. Following step 7012, flowchart 7000 proceedsto step 7014.

In step 7014 of the present embodiment, a demodulated output data sampleis communicated to a correction device. Step 7014 is implemented, in oneembodiment, by communicating a real and/or complex portion of thedemodulated output data sample, via line 184 to PACD 118 for furtherprocessing. Following step 7014, flowchart 7000 proceeds to step 7016

In step 7016 of the present embodiment, a phase correction signal iscalculated. Step 7016 is implemented, in one embodiment, using pilotchannel parameter estimator (PCPE) 116, that is coupled in communicationdevice as shown in FIGS. 1C and 1D. In particular, a single PCPE 116 isprovided for each multipath signal configured in a communication device.In this manner, the present invention provides a capability fordiscretely correcting phase error of a multipath signal, based solely onthe phase error of the pilot channel in that multipath signal. FIG. 4provides one embodiment of the composition of PCPE 116. Step 7012 isdescribed in more detail, in one embodiment, in subsequent flowchart7300 of FIG. 7C and in flowchart 7400 of FIG. 7D. Following step 7016,flowchart 7000 proceeds to step 7018

In step 7018 of the present embodiment, a phase correction signal iscommunicated to correction device(s). Step 7018 is implemented, in oneembodiment by communicating the phase correction signal, as determinedby PCPE 116 in step 7016, via line 186 to pilot assisted correctiondevice (PACD) 118 for further processing. Notably, the phase correctionsignal is communicated in a forward direction. In this manner, thepresent invention corrects the phase of a data signal in real time,provided the phase correction signal and the data signal for which itwas calculated are synchronized. Thus, the present invention overcomesthe limitation of a conventional feedback phase correction systemwherein data signals are corrected for a past phase error, e.g., due tofeedback timing. As a result, the fidelity of the data signal is muchgreater than that of a conventional feedback system. Following step7018, flowchart 7000 proceeds to step 7020

In step 7020 of the present embodiment, a demodulated output data sampleis synchronized with a phase correction signal. Step 7020 isimplemented, in one embodiment, by delay buffer 502 of PACD 118 in FIG.5. Step 7020 is described in more detail, in one embodiment, insubsequent flowchart 7500 of FIG. 7F. Following step 7020, flowchart7000 proceeds to step 7022.

Lastly, in step 7022 of the present embodiment, demodulated output datasamples are corrected with a phase correction signal. Step 7022 isimplemented, in one embodiment by PACD 118 of FIG. 5. Step 7020 isdescribed in more detail, in one embodiment, in subsequent flowchart7500 of FIG. 7F. Following step 7022, flowchart 7000 ends.

Referring now to FIG. 7B, a flowchart of a process to demodulate anextended and long code from a received signal is shown, in accordancewith one embodiment of the present invention. Flowchart 7100 providesexemplary steps for implementing demodulation step 7008 of Flowchart7000 in FIG. 7A. Flowchart 7100 is implemented primarily in ELCD 112 ofFIG. 2. By providing a configurable demodulating code sequence and aconfigurable integration length, the present invention provides aprocess capable of demodulating a wide range of user and/or extendedcode modulation schemes. Consequently, flowchart 7100 provides stepsthat can effectively accommodate a wide range of existing and futureproprietary or non-proprietary algorithms.

In step 7102 of the present embodiment, a signal is received fordemodulation, e.g., in-phase and quadrature-phase signal inputs 7102 aand 7102 b respectively. Step 7102 is implemented, in one embodiment, byreceiving a complex digital signal at ELCD 112 via line 105, fromfront-end processing block 103, as shown in FIG. 1A and FIG. 2. Receivedsignal, referred to as a complex channel signal or an encoded datasignal, is communicated to two branches to provide the same complexdigital signal at first multiplier 200 and second multiplier 201. Thetwo branches reflect the parallel processing of complex digital signalto obtain a real sample and a complex sample. Following step 7102,flowchart 7100 proceeds to step 7103.

In step 7103 of the present embodiment, a product code is received asinput 7103 a for a real product code and 7103 b for a complex productcode. Step 7103 is implemented, in one embodiment, by receiving a firstproduct code of C_(p)×C_(PNLong) 162 a at multiplier-logic device 200 inthe first branch, and by receiving a second product codeC_(q)×C_(PNLong) 162 b at multiplier-logic device 201 in the secondbranch. The configuration of product code inputs 162 a and 162 b of FIG.2 is dictated by ELCD code configuration input 162 to communicationdevice 100 a in FIG. 1, which in turn is provided by an outside sourcesuch as a wireless service provider. Each of these product codes are infact the product of the extended code and long codes used at thetransmitter. Product codes are provided by a code generator unit (CGU),e.g., CGU 140 of FIG. 1A. In another embodiment, an extended codesequence is not utilized in a transmission technique, and thus only auser code would be utilized in step 7103 for inputs 162 a and 162 b. Inyet another embodiment, no user or extended code modulation is utilizedin a transmission technique. In this embodiment, a product code inputs162 a and 162 b are all ones (1) in order to effectively bypass extendedand long code demodulation operations of flowchart 7100. In this manner,the present invention provides for modulation techniques for existingand future extended and user, or long code, channel modulationtechniques. Following step 7103, flowchart 7100 proceeds to step 7104.

In step 7104 of the present embodiment, the complex channel signal ismultiplied by a product code. Step 7104 is implemented in one embodimentby multiply-logic devices 200 and 201, which multiply the complexchannel signal by the respective first and second product codes. Theproduct that is output from multiply-logic devices 200 and 201 isreferred to as a first and second code demodulated sequence, outputs7105 a and 7105 b, respectively, each of which have in-phase and/orquadrature phase components. The multiply operation is performed onmultiple bit samples in the present embodiment, though it is alsoperformed on single-bit samples in another embodiment. Notably, ELCD 112can include configurable sub components that allow differentcombinations of multiplication operations for step 7104 to be performedbetween the real and complex channel signal on line 105 and the real andcomplex code sequence inputs 162 a and 162 b. This configurabiltiyprovides the present invention with an even greater scope ofaccommodating multiple transmission despreading and demodulatingtechniques. Following step 7104, flowchart 7100 proceeds to step 7106.

In step 7106 of the present embodiment, the code-demodulated sequence issummed. Step 7106 is implemented, in one embodiment, by configurableaccumulate and dump circuits 204 and 205. More specifically,configurable accumulate and dump circuit 204 of the first branchaccumulates the code demodulated sequence provided by multiply-logicdevice 200 from step 7104. Similarly, configurable accumulate and dumpcircuit 205 in the second branch accumulates the code demodulatedsequence provided by multiply-logic device 201 from step 7104. Firstconfigurable accumulate and dump circuit 204 produces a firstcode-demodulated sample, while second configurable accumulate and dumpcircuit 204 produces a second code-demodulated sample.

Step 7106 receives an integration length input 7106 a that provides thedesired quantity of accumulate operations to occur before a dumpoperation occurs. Input 7106 a is implemented in the present embodimentby ELCD 112 observation length input 152 to communication device 100 aof FIG. 1A, and subsequent forwarding to configurable accumulate anddump circuits 204 and 205 of FIG. 2. In one embodiment, a quantity ofaccumulate operations may be, for example 10 chips per sample, asdefined by a given transmission technique used for extended and/or longcode modulation. In this embodiment, integration length input 7106 awould be a value of 10 cycles or interactions over which anaccumulation, or integration operation, would occur. In anotherembodiment, an extended code sequence is not utilized in a transmissiontechnique, and thus only a user code would be utilized in step 7106 forinputs 152. In yet another embodiment, no user or extended codemodulation is utilized in a transmission technique. In this latterembodiment, an observation length input 7106 a is unity, e.g., 1, thuspassing each chip through ELCD 112 without integrating them together.This latter embodiment effectively bypasses extended and long codedemodulation operations of flowchart 7100. In this manner, the presentinvention provides for existing and future modulation techniques inextended and user, or long code, channel modulation techniques. Thisconfigurabiltiy allows the receiver, e.g., communication device 100 a todemodulate different modulation and spreading techniques utilized at atransmitter. Consequently, the present invention is capable of beingconfigured to demodulate a wide variety of communication techniques.Following step 7106, flowchart 7100 proceeds to step 7108.

In step 7108 of the present embodiment, cycles are counted. Step 7108 isimplemented, in one embodiment by a counter device, e.g., 654, asapplied to a configurable accumulate and dump circuit, e.g., circuit204. Step 7108 counts local clock cycles applicable to ELCD 112.Following step 7108, flowchart 7100 proceeds to step 7110.

In step 7110 of the present embodiment, an inquiry determines whetherthe cycles counted match an observation length. If the cycles counted domatch the observation length, then flowchart 7100 proceeds to step 7112.However, if cycles counted do not match the observation length, thenflowchart proceeds to step 7114. Step 7110 is implemented, in oneembodiment, by a single comparator, e.g., 656, as applied to bothconfigurable accumulate and dump circuits 204 and 205. In an alternativeembodiment, each sum and dump circuit 204 and 205 has a comparator. Step7110 provides the logic to determine when the desired observation lengthhas been satiated.

Step 7112 arises if the cycles counted do not match an observationlength, per step 7110. In step 7112 of the present embodiment, thesystem increments. Step 7112 is implemented, in one embodiment, by alocal clock cycling as an input 665 to counter 654 as shown in FIG. 6.Following step 7112, flowchart 7100 returns to step 7102.

Step 7114 arises if the cycles counted match an observation length, perstep 7110. In step 7114 of the present embodiment, the sums are dumped.Step 7114 is implemented, in one embodiment, by comparator, e.g., 656,providing an enable signal that dumps an accumulated sum in integrator,e.g., integrator 658, of configurable integrate and dump device 306, asshown in FIG. 6. Thus, a first and second code demodulated sample output7114 a and 7114 b is produced. An intrinsic part of step 7114 is toreset counter 654 for step 7108 for flowchart 7100 to repeat ab initio.Following step 7114, flowchart 7100 ends.

Referring now to FIG. 7C, a flowchart of a process to demodulate atraffic channel code from a received signal is shown, in accordance withone embodiment of the present invention. Flowchart 7200 providesexemplary steps for implementing demodulation step 7012 of Flowchart7000 in FIG. 7A. Flowchart 7200 is implemented primarily in TCD 114 ofFIG. 3. By providing a configurable traffic channel code sequence and aconfigurable integration length, the present invention provides aprocess capable of demodulating a wide range of transmission modulationschemes. The variety of transmission modulation schemes also accountsfor backwards compatibility to transmission techniques that do not usetraffic channel encoding. Consequently, flowchart 7200 provides stepsthat can effectively accommodate a wide range of existing and futureproprietary and non-proprietary algorithms.

In step 7202 of the present embodiment, a code-demodulated sample isreceived. Step 7202 is implemented, in one embodiment, by receiving afirst code demodulated sample 7114 a and a second code demodulatedsample 7114 b. These samples are transmitted from ELCD 112 on inputlines 180 and 182 to traffic channel demodulator (TCD) 114 of FIG. 3, inthe present embodiment. The code-demodulated samples can each have onlyin-phase components or in-phase and quadrature components. Followingstep 7202, flowchart 7200 proceeds to step 7204.

In step 7204 of the present embodiment, a traffic code sequence isreceived. Step 7204 is implemented, in one embodiment, by receiving thesame traffic channel code sequence 164 a at both multipliers 302 and304. In the present embodiment, traffic channel code sequence is a shortWalsh code W_(d)(n). However, the present invention is well suited tousing any traffic code as dictated by TCD code configuration input 164provided to communication device 100 a, e.g., per a user'sspecification. Code sequence input 164 a is provided by a CGU, e.g., CGU140, in the present embodiment. In one embodiment, no traffic channelcode is utilized in a transmission technique. In this embodiment, atraffic channel code of all ones (1) can be provided to effectivelybypass traffic channel demodulation. In this manner, the presentinvention provides for modulation techniques for existing and futuretraffic channel modulation techniques. And the present inventionprovides backwards compatibility for legacy protocols that do not usetraffic channel modulation. Following step 7204, flowchart 7200 proceedsto step 7206.

In step 7206 of the present embodiment, a code-demodulated sample ismultiplied with a traffic code sequence. Step 7206 is implementedsimilarly to step 7104 from flowchart 7100, but uses multiply-logicdevices 302 and 304 of FIG. 3 to produce a first demodulated datasequence output 7206 a and second demodulated data sequence 7206 b,respectively. Following step 7206, flowchart 7200 proceeds to step 7208.

In step 7208 of the present embodiment, the code-demodulated sequence issummed. Step 7208 is similar to step 7106 from flowchart 7100, but isimplemented in the present embodiment by configurable accumulate anddump circuits 306 and 308 to produce a first and a second intermediatedemodulated data sample, respectively. Both the first and secondintermediate demodulated data sample can have an in-phase component anda quadrature-phase component. Step 7208 receives an integration lengthinput 7208 a that provides the desired quantity of accumulate operationsto occur before a dump operation occurs. Consequently, the presentinvention is capable of being configured to demodulate a wide variety oftraffic channel modulation techniques. Following step 7208, flowchart7200 proceeds to step 7210.

In step 7210 of the present embodiment, cycles are counted. Step 7210 isimplemented similarly to 7108 of flowchart 7100, but uses a counterdevice, e.g., counter 654, as applied to configurable accumulate anddump circuits 306 and 308. Following step 7210, flowchart 7200 proceedsto step 7212.

In step 7212 of the present embodiment, an inquiry determines whethercycles match pilot filter length. If the cycles counted do match theobservation length, then flowchart 7200 proceeds to step 7216. However,if cycles counted do not match the observation length, then flowchartproceeds to step 7213. Step 7212 is implemented similarly to 7110 offlowchart 7100, but uses a single comparator, e.g., comparator 656, asapplied to both configurable accumulate and dump circuits 306 and 308.

In step 7216 of the present embodiment, the sums from the configurableaccumulate and dump circuits are dumped. Step 7216 is similar to step7114 of flowchart 7100, but is implemented in the present embodiment bya comparator, e.g., comparator 656, providing an enable signal toconfigurable accumulate and dump circuits 306 and 308. Step 7216provides an in-phase and a quadrature-phase portion of a firstintermediate demodulated sample 7216 a, and an in-phase and aquadrature-phase portion of a second intermediate demodulated sample7216 b. Following step 7216, flowchart 7200 proceeds to step 7218.

In step 7218 of the present embodiment, an in-phase portion of the firstintermediate demodulated sample is added to a quadrature phase portionof the second intermediate demodulated sample. Step 7218 is implementedsimilarly to 7106 of flowchart 7100, but uses first adder-logic circuit310 for receiving and adding the in-phase portion of the firstintermediate demodulated sample to the quadrature-phase portion of thesecond intermediate demodulated sample. Thus, step 7218 produces ademodulated output data sample 7218 a. Following step 7218, flowchart7200 proceeds to step 7220.

In step 7220 of the present embodiment, an in-phase portion of a secondintermediate demodulated sample is subtracted from a quadrature-phaseportion of a first intermediate demodulated sample. Step 7218 isimplemented similarly to 7218, but subtracts the in-phase portion of thesecond intermediate demodulated sample from the quadrature-phase portionof the first intermediate demodulated sample, using second adder-logiccircuit 312. Thus, step 7220 produces a demodulated output data sample7220 a, which, along with demodulated output data sample 7218 a, ismanaged by interface 314 and provided on output line 184 to subsequentdemodulator components. The operation performed by steps 7218 and 7220can be referred to as an inner-product operation. Following step 7218,flowchart 7200 proceeds to step 7220.

Referring now to FIG. 7D, a flowchart of a process to estimateparameters of a pilot channel is shown, in accordance with oneembodiment of the present invention. Flowchart 7300 provides exemplarysteps for implementing phase correction step 7016 of Flowchart 7000 inFIG. 7A. Flowchart 7300 is implemented primarily in PCPE 116 of FIG. 4.By providing a process by which the phase of the pilot signal can beestimated, the present invention provides a source of error correctionsignal for configurable demodulator 110-1 of FIG. 1A.

PCPE 116 takes the outputs of ELCD 112, and performs open-loop phaseestimation. The unmodulated pilot signal is tracked in an open loopchannel estimator 402-406 followed by FIR filters 408, 410, integratingover an interval N_(p), called the pilot filter length. It can be shownthat the acquisition and tracking performance of the system is stronglydependent on N_(p) and the pilot-channel energy, and this architecturerealizes a quasi-coherent detector. This approach is superior to aclosed loop phase tracking process, which suffers from the well-knownweakness of cycle slipping, especially in fading channels. Theperformance of this approach in highly mobile environments is dependenton the amount of energy devoted to the pilot channel.

In step 7352 of the present embodiment, a signal is received. Step 7352is implemented similarly to 7202 of flowchart 7200, but implemented byreceiving the first code demodulated sample 7114 a and the second codedemodulated sample 7114 b at PCPE 116, as shown in FIG. 4. Followingstep 7352, flowchart 7300 proceeds to step 7354.

In step 7354 of the present embodiment, the received signal isdemodulated with a pilot sequence. Step 7354 is implemented in oneembodiment by PCPE 116 of FIG. 4. Step 7354 receives a pilot sequenceinput 7354 a for the demodulation. Input 7354 a is implemented by pilotcode input 166 a provided to multipliers 402 and 404 of FIG. 4. Step7354 produces a first demodulated intermediate sample output 7354 b anda second demodulated intermediate sample output 7354 c. Output 7354 band 7354 c is provided to interface 406 and 408 of FIG. 4. Additionaldetail for implementing step 7354 is provided in steps 7402 through 7404of subsequent flowchart 7400 in FIG. 7E. Following step 7354, flowchart7300 proceeds to step 7356.

In step 7356 of the present embodiment, open-loop channel estimation isperformed. Step 7356 is implemented, in one embodiment, using PCPE 116of FIG. 4. Step 7012 is described in more detail, in one embodiment, bysteps 7406 through 7412 of subsequent flowchart 7400 of FIG. 7E.Following step 7356, flowchart 7300 proceeds to step 7358.

In step 7358 of the present embodiment, the signals from open-loopchannel estimation are filtered separately. An input of filterobservation length 7358 a provides configurabiltiy to step 7358. Step7358 is implemented, in one embodiment, by pilot filter blocks 416 and418 of PCPE 116 in FIG. 4. Step 7012 is described in more detail, in oneembodiment, by steps 7414 through 7418 of subsequent flowchart 7400 inFIG. 7E. Following step 7358, flowchart 7300 ends.

Referring now to FIG. 7E, a flowchart of a more detailed process toestimate parameters of a pilot channel is shown, in accordance with oneembodiment of the present invention. Flowchart 7400 provides exemplarysteps for implementing demodulation, open-loop channel estimation, andfiltering steps 7354 through 7358 of flowchart 7300 in FIG. 7D.

In step 7402 of the present embodiment, a first code demodulated sampleand a second code-demodulated sample are multiplied by a pilot sequence.Step 7402 is implemented in the present embodiment by multiplying thereceived first code demodulated sample 7114 a and second codedemodulated sample 7114 b with an appropriate pilot code sequence, e.g.,pilot sequence input 7354 a as shown in step 7354. Pilot code sequenceinput 166 a is provided to multiplier-logic devices 402 and 404 of PCPE116, as dictated by configured input PCPE code configuration 166 of FIG.1C and 1D. Interface blocks 406 and 408 provide the in-phase portion andthe quadrature-phase portion, e.g., via buffering, of the pilotdemodulated sequence that is output from both multipliers 402 and 404.Following step 7402, flowchart 7400 proceeds to step 7406.

In step 7406 of the present embodiment, an in-phase portion of firstintermediate sample is added to a quadrature-phase portion of secondversion to produce a first phase correction sequence. Step 7406 isimplemented similarly to 7218 of flowchart 7200, but performs an addoperation at adder-logic device 410. Following step 7406, flowchart 7400proceeds to step 7408.

In step 7408 of the present embodiment, a quadrature-phase portion offirst intermediate sample is subtracted from in-phase portion of thesecond intermediate sample to get second phase correction sequence. Step7408 is implemented similarly to step 7406, but uses adder-logic device412 for the subtraction operation. Following step 7408, flowchart 7400proceeds to step 7412.

In step 7412 of the present embodiment, the first phase correctionsequence is summed at the first filter and the second phase correctionsequence is summed at the second filter. An input of filter observationlength 7358 a is provided for step 7412 similar to that provided to step7358 of flowchart 7400. Step 7412 is implemented, in one embodiment, byconfigurable filter circuits 416 and 418 of FIG. 4. More specifically,configurable filter circuit 416 accumulates the phase correctionsequence provided by add-logic device 410 from step 7406. Similarly,second configurable filter circuit 418 accumulates the code demodulatedsequence provided by multiply-logic device 201 from step 7104. Firstconfigurable filter 416 and second configurable filter 418 can alsoperform other filtering operations such as weighting by a preset or avariable factor, e.g., provided with input PCPE filter length 156 ofFIG. 1A. Step 7412 receives a filter length input 7412 a that dictatesthe desired quantity of accumulate operations to occur before a dumpoperation occurs, as dictated by PCPE filter length 156 provided tocommunication device 100 a. This configurabiltiy allows the presentinvention to accommodate different transmission protocols used for thepilot sequence. Consequently, the present invention is capable of beingconfigured to adjust phase error over a wide variety of communicationprotocols. Following step 7412, flowchart 7400 proceeds to step 7414.

In step 7414 of the present embodiment, cycles are counted. Step 7414 isimplemented similarly to step 7210 of flowchart 7200, but implementscounter device, e.g., 654, for configurable pilot circuits 416 and 418.Step 7414 counts clock cycles local to PCPE 116. Following step 7414,flowchart 7400 proceeds to step 7416.

In step 7416 of the present embodiment, an inquiry determines whethercycles match pilot filter length. Step 7416 is implemented similarly tostep 7212 of flowchart 7200, but applies a single comparator, e.g., 656,to both configurable filter circuits 416 and 418. However, if the cyclescounted do match the filter length for step 7416, then flowchart 7400proceeds to step 7417. Alternatively, if the cycles counted do not matchthe observation length, then flowchart proceeds to step 7418.

In step 7417, the system is incremented. Step 7417 is implementedsimilarly to 7112 of flowchart 7100, but uses a single comparator forthe present step, e.g., comparator 656, as applied to both configurablefilter circuits 416 and 418. Following step 7417, flowchart 7400 returnsto step 7402.

In step 7418 of the present embodiment, a phase correction sample fromfirst filter and second accumulator are dumped. Step 7418 is implementedsimilarly to step 7216 of flowchart 7200. However the present embodimentuses a comparator, e.g. 656 to provide an enable signal on enable lineof pilot filter circuits 416 and 418 to dump an in-phase portion of thephase correction sample and a quadrature-phase portion of the phasecorrection sample, respectively. Step 7418 results in an in-phasedemodulated correction sample output 7418 b and a quadrature-phasedemodulated correction sample output 7418 a. Step 7114 includes a substep of resetting counter 654 such that flowchart 7100 can repeat abinitio. Following step 7418, flowchart 7400 ends.

Referring now to FIG. 7F, a flowchart of a process to correct phaseerror in a received signal via a feed forward phase correction signal isshown, in accordance with one embodiment of the present invention.Flowchart 7500 provides exemplary steps for implementing demodulationstep 7020-8022 of flowchart 7000 in FIG. 7A. Flowchart 7500 isimplemented primarily in PACD 118 of FIG. 5. By providing a process forcorrecting phase error of a data signal by using a feed forward errorcorrection signal, the present invention provides a demodulator thatcorrects a given data value with its properly sequenced phase error, asdetermined by the pilot signal associated with that data value. Thus,the present invention provides significantly higher performance duringthe demodulation operation.

In step 7502 of the present embodiment, a traffic-demodulated signal isreceived. Step 7502 is implemented, in one embodiment, by communicatingdemodulated output data sample from TCD 114 to PACD 118 via line 184, asshown in FIGS. 1C, 1D, and 5. Following step 7502, flowchart 7500proceeds to step 7504.

In step 7504 of the present embodiment, a traffic-demodulated signal isdelayed. A delay value input 7504 a is received in step 7504 to indicatethe desired delay. Step 7504 is implemented in one embodiment by delaybuffer 502, which receives a delay input 158 that dictates the desirednumber of samples or cycles to buffer, or hold, prior to passing them onto the next process. In particular, delay input is dictated by PACDdelay 158 provided to communication device 100 a, as shown in FIG. 1A.This configurabiltiy allows the present invention to accommodatedifferent transmission techniques that have an effect on amount of timeor cycles needed to perform the phase error estimation process.Consequently, the present invention is capable of being configured toadjust the delay over a wide variety of communication protocols, giventhe amount of memory buffer available in buffer block 502. In thepresent embodiment, the delay is equivalent to the total processingdelay time incurred by PCPE 116. In this embodiment, the delay issufficiently small so as not to adversely affect performance of theoverall communication device. However, in another embodiment, delay 7504a is either greater or less than the total processing delay timeincurred by PCPE 116, as determined by a given application or userspecification, e.g., PACD delay input 158 of FIG. 1A. Following step7504, flowchart 7500 proceeds to step 7506.

In step 7506 of the present embodiment, a phase correction signal isreceived. Inputs 7418 a and 7418 b are the quadrature-phase demodulatedcorrection sample, and the in-phase demodulated correction sample,respectively, from step 7418 of flowchart 7400. Step 7506 isimplemented, in one embodiment, by receiving phase correction samplefrom PCPE 116 at PACD 118 via line 186, as shown in FIG. 1C, 1D, andFIG. 5. Received signal is a feed forward because it travels in thedirection of the data signal processing operations. By delaying thedemodulated output data sample, the phase correction signal has anopportunity to synchronize with the appropriate point of the data signalfor which the phase error was determined. Thus, the present inventionprovides a very accurate and efficient method of correcting phase errorin a data signal. Following step 7506, flowchart 7500 proceeds to step7508.

In step 7508 of the present embodiment, a traffic-demodulated signal ismultiplied by the phase correction signal is. Step 7508 is implementedsimilarly to step 7206 of flowchart 7200, but using multiply logicdevice 506. The product that is output from multiply-logic device 506has been corrected for the measured phase error in the pilot channel.The phase correction is performed for the specific phase error in agiven multipath signal, and thus overcomes the limitations ofconventional phase error adjustment based on an average phase error overmultiple multipath signals. Following step 7508, flowchart 7500 proceedsto step 7510.

In step 7510 of the present embodiment, a real output is provided. Step7510 is implemented in the present embodiment by memory registers inreal block 508 of FIG. 5. In this manner, the in-phase andquadrature-phase data values that have been corrected for error areavailable to subsequent processing blocks, e.g., block 119, incommunication device 100 a. These subsequent processing blocks can theninterpret the phase-corrected in-phase portion and quadrature-phaseportion of the data values, e.g., per an m-ary constellation. Followingstep 7510, flowchart 7500 ends.

While flowcharts 7000-8500 of the present embodiment show a specificsequence and quantity of steps, the present invention is suitable toalternative embodiments. For example, not all the steps provided inflowcharts 7000-8500 are required for the present invention. Forexample, flowchart 7000 provides steps 7012 for demodulating a trafficcode channel. However, if a transmission technique does not utilize atraffic code channel, then step 7012 may be omitted, or neutralized, inone embodiment. Similarly, other steps may be omitted depending upon theapplication. In contrast, the present invention is well suited toincorporating additional steps to those presented, as required by anapplication, or as desired for permutations in the process.

Lastly, the sequence of the steps for flowcharts 7000-8500 can bemodified depending upon the application. Thus, while flowcharts7000-8500 are shown as a single serial process, they can also beimplemented as a continuous or parallel process. For example, it isappreciated that flowcharts 7000-8500 can be repeated for the multiplehardware kernel planes, e.g., plane 110-1 through 110-N, ofcommunication device 100 a of FIG. 1A.

Many of the instructions for the steps, and the data input and outputfrom the steps, of flowcharts 7000-8500 utilize memory and processorhardware components, e.g., memory 120, and processor 130, per FIG. 1A.The memory storage used to implement the flowchart steps in the presentembodiment can either be permanent, such as read only memory (ROM), ortemporary memory such as random access memory (RAM). Memory storage canalso be any other type of memory storage, capable of containing programinstructions such as flash memory. Similarly a processor used toimplement the flowchart steps can either be a dedicated controller, anexisting system processor, e.g., processor 130 of FIG. 1A, a localprocessor, e.g., processor or controller 172 of FIG. 1D, or it can be adedicated digital signal processing (DSP) processor, as appropriate forthe type of step. Alternatively, the instructions may be implementedusing some form of a state machine.

Some portions of the detailed description, e.g., the processes, arepresented in terms of procedures, logic blocks, processing, and othersymbolic representations of operations on data bits within a computer ordigital system memory or on signals within a communication device. Thesedescriptions and representations are the means used by those skilled inthe digital communication arts to most effectively convey the substanceof their work to others skilled in the art. A procedure, logic block,process, etc., is herein, and generally, conceived to be aself-consistent sequence of steps or instructions leading to a desiredresult. The steps are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these physicalmanipulations take the form of electrical or magnetic signals capable ofbeing stored, transferred, combined, compared, and otherwise manipulatedin a communication device or a processor. For reasons of convenience,and with reference to common usage, these signals are referred to asbits, values, elements, symbols, samples, characters, terms, numbers, orthe like with reference to the present invention.

It should be borne in mind, however, that all of these terms are to beinterpreted as referencing physical manipulations and quantities and aremerely convenient labels to be interpreted further in view of termscommonly used in the art. Unless specifically stated otherwise asapparent from the following discussions, it is understood thatthroughout discussions of the present invention, terms such as“receiving,” “demodulating,” “performing,” “filtering,” “receiving,”“dumping,” “multiplying,” “providing,” “adding,” “subtracting,”“delaying,” “summing,” “accumulating,” “comparing,” “converting,”“processing,” “feeding,” “generating,” “synchronizing,” “transmitting,”“correcting,” “formatting,” or the like, refer to the action andprocesses of a communication device or a similar electronic computingdevice, that manipulates and transforms data. The data is represented asphysical (electronic) quantities within the communication devicescomponents, or the computer system's registers and memories, and istransformed into other data similarly represented as physical quantitieswithin the communication device components, or computer system memoriesor registers, or other such information storage, transmission or displaydevices.

In view of the embodiments presented herein, the present inventioneffectively provides a method and apparatus that overcomes thelimitations associated with the varied hardware, software, andmethodology of demodulating digital signals in each of the varied spreadspectrum applications. Furthermore, the embodiments provided hereinillustrate how the present invention corrects the phase error in areceived signal. Lastly, the present embodiments illustrate how thepresent invention overcomes the limitations in conventional analog phasecorrection system. In particular, the embodiments explain how thepresent invention overcomes some of the major limitations of aconventional feedback system.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that the specificdetails are not required in order to practice the invention. In otherinstances, well-known circuits and devices are shown in block diagramform in order to avoid unnecessary distraction from the underlyinginvention. Thus, the foregoing descriptions of specific embodiments ofthe present invention are presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, obviously many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, the therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

1. A configurable parameter estimator for a pilot channel, the parameterestimator comprising: an open-loop channel estimator for performing anopen-loop phase estimation; a first filter coupled to the parameterestimator for a pilot channel, the first filter for integrating a firstsignal from the open-loop channel estimator; and a second filter coupledto the parameter estimator for a pilot channel, the second filter forintegrating a second signal from the open-loop channel estimator, thefirst filter and the second filter providing an error-correcting signal,wherein the first filter and the second filter have a variable pilotfilter length.
 2. The configurable parameter estimator recited in claim1 wherein the first filter provides anin-phase of the error correctingsignal, and the second filter provides a quadature-phase of the errorcorrecting signal.
 3. A configurable parameter estimator for a pilotchannel, the parameter estimator comprising: an open-loop channelestimator for performing an open-loop phase estimation, wherein theopen-loop channel estimator comprises: a first interface for providingan in-phase portion and a quadrature-phase portion of a first pilotdemodulated sequence; a second interface for providing the in-phaseportion and the quadrature-phase portion of a second pilot demodulatedsequence; a first adder coupled to the first interface and the secondinterface, the first adder for adding the in-phase portion of the firstpilot demodulated sequence and the quadrature-phase portion of thesecond pilot demodulated sequence; and a second adder coupled to thefirst interface and the second interface, the second adder forsubtracting the quadrature-phase portion of the first pilot demodulatedsequence from the in-phase portion of the second pilot demodulatedsequence; a first filter coupled to the parameter estimator, the firstfilter for integrating a first signal from the open-loop channelestimator; and a second filter coupled to the parameter estimator, thesecond filter for integrating a second signal from the open-loop channelestimator, the first filter and the second filter providing anerror-correcting signal.
 4. The configurable parameter estimator recitedin claim 3 further comprising: a multiplier coupled to the firstseparator, the multiplier for multiplying a pilot code times thein-phase portion of the code-demodulated sample to create the firstpilot demodulated sequence.
 5. The configurable parameter estimatorrecited in claim 3 further comprising: a multiplier coupled to thesecond separator, the multiplier for multiplying a pilot code times aquadrature-phase portion of the code-demodulated sample to create thesecond pilot demodulated sequence.
 6. A configurable parameter estimatorfor a pilot channel, the parameter estimator comprising: an open-loopchannel estimator for performing an open-loop phase estimation; a firstfilter coupled to the parameter estimator, the first filter forintegrating a first signal from the open-loop channel estimator; and asecond filter coupled to the parameter estimator, the second filter forintegrating a second signal from the open-loop channel estimator, thefirst filter and the second filter providing an error-correcting signal,wherein the first filter and the second filter are a finite impulseresponse (FIR) that produce an in-phase correction sample and aquadrature-phase correction sample, respectively.
 7. In a configurableparameter estimator, a method for estimating an error in a pilotchannel, the method comprising: a) receiving a first code demodulatedsample and a second code-demodulated sample, each having an in-phase anda quadrature-phase component; b) demodulating the first code demodulatedsample and the second code demodulated sample with a pilot codesequence; c) performing an open-loop channel estimate on the first andsecond code demodulated samples using an open-loop channel estimator; d)filtering a first signal from the open-loop channel estimator at a firstfilter; e) filtering a second signal from the open-loop channelestimator at a second filter, wherein the first signal and the secondsignal represent an error correction signal for the pilot channel; andf) receiving a value specifying a variable pilot filter length using thefirst filter and the second filter.
 8. The method recited in claim 7further comprising: g) dumping a first sample from the first filter anda second sample from the second filter when the variable pilot filterlength has been satisfied.
 9. The method recited in claim 7 wherein thefirst filter provides an in-phase of the error correction signal, andthe second filter provides a quadature-phase of the error correctionsignal.
 10. In a configurable parameter estimator, a method forestimating an error in a pilot channel, the method comprising: a)receiving a first code demodulated sample and a second code-demodulatedsample, each having an in-phase and a quadrature-phase component; b)demodulating the first code demodulated sample and the second codedemodulated sample with a pilot code sequence, wherein the demodulatingstep b) comprises: b1) multiplying the first code demodulated samplewith the pilot code sequence to create a first intermediate sequence;b2) multiplying the second code demodulated sample with the pilot codesequence to create a second intermediate sequence b3) providing anin-phase portion and a quadrature-phase portion of the firstintermediate sequence at a first interface; b4) providing an in-phaseportion and a quadrature-phase portion of the second intermediatesequence at a second interface; b5) adding the in-phase portion of thefirst intermediate sequence with the quadrature-phase portion of thesecond intermediate sequence at a first adder; and b6) subtracting thequadrature-phase portion of the first intermediate sequence from thein-phase portion of the second intermediate sequence at a second adder;and c) performing an open-loop channel estimate on the first and secondcode demodulated samples using an open-loop channel estimator.
 11. Aconfigurable parameter estimator for a pilot channel, the parameterestimator comprising: an open-loop channel estimating means forperforming an open-loop phase estimation; a first filter means, which iscoupled to the parameter estimator for a pilot channel, for integratinga first signal from the open-loop channel estimating means; and a secondfilter means, which is coupled to the parameter estimator for a pilotchannel, for integrating a second signal from the open-loop channelestimating means, wherein the first and second filters provide a phaseerror correction signal, and wherein the first filter means and thesecond filter means have a variable pilot filter length.
 12. Theconfigurable parameter estimator recited in claim 11 wherein the firstfilter means provides an in-phase of the error correction signal, andthe second filter means provides a quadature-phase of the errorcorrection signal.
 13. A configurable parameter estimator for estimatingan error in a pilot channel, comprising: a receiving means for receivinga first code demodulated sample and a second code-demodulated sample,each having an in-phase and a quadrature-phase component; a demodulatingmeans for demodulating the first code demodulated sample and the secondcode demodulated sample with a pilot code sequence; means for performingan open-loop channel estimate on the first and second code demodulatedsamples using an open-loop channel estimating means; means for filteringa first signal from the open-loop channel estimator at a first filter;means for filtering a second signal from the open-loop channel estimatorat a second filter, wherein the first signal and the second signalrepresent an error correction signal for the pilot channel; and meansfor receiving a value specifying a variable pilot filter length usingthe first filter and the second filter.
 14. The configurable parameterestimator recited in claim 13 wherein the means for filtering a firstsignal provides an in-phase of the error correction signal, and themeans for filtering a second signal provides a quadature-phase of theerror correction signal.
 15. A configurable parameter estimator for apilot channel, the parameter estimator comprising: a channel estimatorfor performing a phase estimation; a first filter, which is coupled tothe parameter estimator for a pilot channel, configured to integrate afirst signal from the channel estimator; and a second filter, which iscoupled to the parameter estimator for a pilot channel, configured tointegrate a second signal from the channel estimator, wherein the firstand second filters have a variable pilot filter length and provide aphase error correction signal.
 16. The configurable parameter estimatorrecited in claim 15 wherein the first filter provides an in-phase of theerror correction signal, and the second filter provides aquadature-phase of the error correction signal.
 17. In a parameterestimator, a method for estimating an error in a pilot channel, themethod comprising: a) receiving a first code demodulated sample and asecond code-demodulated sample, each having an in-phase and aquadrature-phase component; b) demodulating the first code demodulatedsample and the second code demodulated sample with a pilot codesequence; c) performing a channel estimate on the first and second codedemodulated samples using a channel estimator; d) filtering a firstsignal from the open-loop channel estimator at a first filter; e)filtering a second signal from the open-loop channel estimator at asecond filter, wherein the first signal and the second signal representan error correction signal for the pilot channel; and f) receiving avalue specifying a variable pilot filter length using the first filterand the second filter.
 18. The method recited in claim 17 furthercomprising: f) dumping a first sample from the first filter and a secondsample from the second filter when the variable pilot filter length hasbeen satisfied.
 19. The method recited in claim 17 wherein the firstfilter provides an in-phase of the error correction signal, and thesecond filter provides a quadature-phase of the error correction signal.